Diffusion sheet and manufacturing method thereof

ABSTRACT

A diffusion sheet structure in the direct type backlight module with anti-UV rays function and its manufacturing method discloses a diffusion sheet in the backlight module applied to TFT-LCD TV, and plural layer of the diffusion sheet made by a method of a multi-layer co-extrusion. The diffusion sheet advocates that while producing diffusion layer, at least a ultra-violet rays absorption layer set on the surface of diffusion layer at the same time to achieve insulating ultra-violet rays directly irradiated on the diffusion sheet and to avoid yellow and pyrolysis phenomenon occurred on the diffusion sheet. These results in avoiding the deviation caused from color temperature and chromaticity coordinate of TFT-LCD TV because of yellow diffusion sheet, then to achieve the purpose of improving product quality and materials lifespan.

RELATED APPLICATIONS

This application is a Continuation patent application of co-pendingapplication Ser. No. 10/863,490, filed on 9 Jun. 2004

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a diffusion sheet structure in thedirect type backlight module with anti-UV rays function and itsmanufacturing method, which especially points at a diffusion sheet inthe backlight module applied to TFT-LCD TV. This invention explores adiffusion sheet with a ultra-violet rays absorption layer avoid yellowand pyrolysis phenomenon and finally to improve product quality andmaterials lifespan.

2. Description of the Prior Art

Since TFT-LCD has been invented, all kinds of colour monitor have beenwidely applied in the daily life, such as notebook, PC monitor, colourmobile phone, PDA, and LCD TV etc., which have accordingly replacedconventional display such as CRT, TN and STN. An example of TFT-LCD TV,TFT-LCD TV being accordingly accepted by the consumers is because ofliquid crystal panel producing technology improvement, such as shortresponse time, high resolution, and higher yield of large panel.Besides, higher brightness of backlight module is also one of the mainfactors.

The larger size of TFT-LCD TV requires more, the higher brightness ofone requires more. Normally the brightness of TFT-LCD TV requires800-1200 Cd/m², moreover, the uniform backlight module technologythrough light guide panel by the traditional edge light source can notsatisfy the requirements of TFT-LCD TV. Therefore, high brightness ofdirect type backlight source is occurred.

In order to enhance the brightness of TFT-LCD TV, it is necessary toincrease the quantity of CCFL (Cold Cathode Fluorescent Lamp) and theedge light source is changed into direct type light source, shown asFIG. 1, which is a schematic diagram of the prior art of direct typebacklight module. As FIG. 1 shown, said direct type backlight module 1′comprises of a reflector 10′, plural light source 20′ and a diffusionsheet 30′. In order to avoid lamp mark, the light guide panel isrequired to be replaced by diffusion sheet to uniformly disperse thebrightness of light source. The thickness of diffusion sheet iscontrolled in a range of 2 to 3 mm, the thickness of relative lightguide panel is a range of 3 to 12 mm which having a large capability ofreducing materials cost and to achieve the purpose of weight. Thepresent diffusion sheet is mainly composed of PMMA (PolymethylMethacrylate), MS (MMA/Styrene Copolymer), PC (Polycarbonate), and COC(Cycle Olefin Copolymer). and adding light diffusion particles in thetransparent substrate to achieve uniform light.

The main strength of diffusion sheet in the composition of PMMA is welloptical transmittance and yellow-resistance, however, the waterabsorption ratio of PMMA is in a range of 0.3 to 0.4% which resulted ina defect of warp and bad dimensional stability on the large TV. Thelight transmittance of MS and PC is small 2 to 3% than PMMA, but MS andPC has good performance on high temperature resistance and dimensionalstability. The main defect is that MS and PC under irradiation of UVrays result in the problem of yellow. If the diffusion sheet in thecomposition of PC is long time irradiated under CCFL, then the problemsof yellow will occur and result in colour temperature and chromaticaberration of panel. This problem is the main reason why diffusion sheetwith PC materials cannot be extensively applied.

Therefore, providing a novel diffusion sheet structure in the directtype backlight module with anti-UV rays function and its manufacturingmethod for the aforesaid problems can not only improve the defects ofyellow of the conventional diffusion sheet which resulted in deviation,but also can be simplified the process. Based on the inventor engagingon the research and develop and sales experiences for the relatedproducts for many years, the inventor finally proposes a method toimprove the aforementioned problems for diffusion sheet structure in thedirect type backlight module with anti-UV rays function and itsmanufacturing method, according to his professional background.

SUMMARY OF THE INVENTION

The primary purpose of the present invention is to provide a diffusionsheet structure in the direct type backlight module with anti-UV raysfunction and its manufacturing method, which using a ultra-violet raysabsorption layer sets on a diffusion layer to achieve insulatingultra-violet rays directly irradiated on the diffusion and to avoidyellow and pyrolysis phenomenon occurred on the diffusion sheet.Furthermore, to avoid the deviation caused from color temperature andchromaticity coordinate of TFT-LCD TV because of yellow diffusion sheet,then to achieve the purpose of improving product quality and materialslifespan.

In order to perform the aforementioned purposes, efficiency andcharacteristics of each, the present invention explores that diffusionsheet structure in the direct type backlight module with anti-UV raysfunction and its manufacturing method, which is a diffusion sheet in thebacklight module applied to TFT-LCD TV, and plural layer of thediffusion sheet made by a method of a multi-layer co-extruder. Thepresent invention advocates that while producing diffusion sheet, atleast a ultra-violet rays absorption layer set on the surface ofdiffusion sheet at the same time to achieve insulating ultra-violet raysdirectly irradiated on the diffusion sheet and to avoid yellow andpyrolysis phenomenon occurred on the diffusion sheet. These results inavoiding the deviation caused from color temperature and chromaticitycoordinate of TFT-LCD TV because of yellow diffusion sheet, then toachieve the purpose of improving product quality and materials lifespan.For manufacturing technology, it is mainly using a co-extruder toproduce multi-layer structure of diffusion sheet which is based on thediffusion sheet that a substrate adding a light diffusion materials, andin a range of 10 to 500 μm thickness of sheet is co-extruded at least onone side of diffusion sheet at the same time, then adding a transparentresin of UV rays absorbent to form at least one side of UV raysabsorbent on said diffusion sheet, therefore, at least one side ofanti-UV rays of diffusion sheet is formed.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is an illustrated diagram of the direct type backlight module ofthe prior art;

FIG. 2 is a schematic diagram of the preferred embodiment of the presentinvention;

FIG. 2A is a schematic diagram of another preferred embodiment of thepresent invention;

FIG. 3 is flowchart of the preferred embodiment of the presentinvention; and

FIG. 4 is a graphic of the preferred embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In order to clearly express and explore the feature characteristics andefficiency of the present invention for the committee of patent, thepreferred embodiment and detailed description is as below.

In order to improve the yellow problems of the prior art which isresulted from UV rays for diffusion sheet of direct type backlightmodule that applied to TFT-LCD TV, the present invention proposes thatsetting a transparent substrate with a UV rays absorbent on the surfaceof diffusion sheet, the thickness of UV rays absorption can becontrolled in a range of 1 to 200 μm. The present invention alsoproposes a process of co-extrusion While diffusion sheet is extruded bythe main extruder, the sub-extruder extrudes UV rays absorption layer atthe same time at least on one side of said diffusion sheet to achievethe effect of insulating UV rays directly irradiating on diffusion sheetto avoid yellow problem.

FIG. 2 is a schematic diagram of the preferred embodiment of the presentinvention that explores diffusion sheet structure of the direct typebacklight module applying to TFT-LCD TV. As shown in FIG. 2, the presentinvention explores a structure of diffusion sheet of the direct typebacklight module with anti-UV rays function. Said diffusion sheet 10comprises at least a UV rays absorption layer 100 and a diffusion sheet110, wherein said UV rays absorption layer 100 is located at least oneside of said diffusion sheet 110, wherein said UV rays absorption layer100 is a UV rays 200 to insulate UV rays directly irradiating on saiddiffusion sheet 10 to avoid the problems of yellow and pyrolysisoccurred on diffusion sheet.

Wherein said UV rays absorption layer 100 comprises a resin 102 which isselected from a transparent acrylic resin and a UV rays absorbent, thethickness of said UV rays absorption layer 100 is in a range of 10 to200 μm. Said diffusion sheet 110 comprises pural light diffusionparticles 112 which is selected from one of organic and inorganicmaterials, such as acrylic resin, Titanium Dioxide (TiO₂), SiliconDioxide (SiO₂), and Silicon and its particle size is in a range of 1˜50μm. And a substrate 114 which is selected from one of acrylic resin,PMMA (Polymethyl Methacrylate), MS (MMA Styrene Copolymer), PC(Polycarbonate) and Cyclo Olefin Copolymer (COC).

Moreover, FIG. 2A is a schematic diagram of another preferred embodimentof the present invention that explores diffusion sheet structure. Asshown in FIG. 2, the present invention explores that said diffusionsheet 10, wherein said UV rays absorption layer 110 can be located onthe top and bottom of said diffusion sheet 120.

FIG. 3 is flowchart of the preferred embodiment of the present inventionthat explores a manufacturing process of diffusion sheet. As shown inFIG. 3, the present invention explores that a method of manufacturingdiffusion sheet in the direct type backlight module with anti-UV rayscomprising the steps of:

-   Step S110: extruding a diffusion layer by adding a plurality of    light diffusion particles into a substrate and using a first    extruder;-   Step S120: extruding a ultra-violet rays absorption layer by adding    a ultra-violet rays absorbent into a resin and using a second    extruder;-   Step S130: taking said ultra-violet rays absorption layer to touch    at least one surface of said diffusion layer by a multi-layer T-die;-   Step S140: co-extruding said diffusion layer and said ultra-violet    rays absorption layer to form a plate structure of light diffusion    sheet with anti-yellow and well dimensional stability.

Among step 110, the content of said light diffusion particles is 10percent of said substrate. Among step 120, the increment of said UV raysabsorbent is 1 to 5% of said resin.

Finally, FIG. 4 is a graphic of the preferred embodiment of the presentinvention that explores diffusion sheet. As shown in FIG. 4, the presentinvention explores that steps of a diffusion sheet and its manufacturingmethod. Firstly, it is mainly using the first extruder 40 adding 10percent of PMMA light diffusion particles 20 of PC resin 30 to extrude adiffusion sheet 50. Secondly, it is using the second extruder 80 adding1 to 5% of UV rays absorbent 60 of transparent resin layer 70 to extrudea UV rays absorption layer 90. Thirdly, said UV rays absorption layer 90is adhered on the top and bottom of diffusion layer 50 throughmulti-layer T-die 95. Finally, said PC diffusion layer 50 and at least aUV rays absorption layer 90 co-extrude a diffusion sheet 98 with platestructure of yellow-resistance and well dimensional stability.

Therefore, the present invention is related to a diffusion sheet and itsmanufacturing method which a diffusion sheet of backlight module appliedto TFT-LCD TV that using a method of multi-layer co-extrusion moldingtechnology produces plural layer diffusion sheet. The present inventionis that while producing diffusion sheet of direct type backlight moduleof TFT-LCD TV, at least a ultra-violet rays absorption layer set on thesurface of diffusion sheet at the same time to achieve insulatingultra-violet rays directly irradiated on the diffusion and to avoidyellow and pyrolysis phenomenon occurred on the diffusion sheet. Theseresults in avoiding the deviation caused from color temperature andchromaticity coordinate of TFT-LCD TV because of yellow diffusion sheet,then to achieve the purpose of improving product quality and materialslifespan.

While certain preferred embodiments of the present invention have beendisclosed in detail, it is to be understood that various modificationsmay be adopted without departing from the spirit of the invention orscope of the following claims.

1. A structure of diffusion sheet in the direct type backlight modulewith anti-UV rays comprising: at least a ultra-violet rays absorptionlayer; and a diffusion layer; wherein said ultra-violet rays absorptionlayer located at least a surface of said diffusion layer.
 2. Thestructure of diffusion sheet in the direct type backlight module withanti-UV rays as claimed in claim 1, wherein said ultra-violet raysabsorption layer comprises a resin and a ultra-violet rays absorbent. 3.The structure of diffusion sheet in the direct type backlight modulewith anti-UV rays as claimed in claim 2, wherein said resin is selectedfrom one of transparency acrylic resin, PMMA (Polymethyl Methacrylate),MS (MMA/Styrene Copolymer) and PC (Polycarbonate), COC (Cycle OlefinCopolymer).
 4. The structure of diffusion sheet in the direct typebacklight module with anti-UV rays as claimed in claim 1, wherein thethickness of said ultra-violet rays absorption layer is 1˜200 μm.
 5. Thestructure of diffusion sheet in the direct type backlight module withanti-UV rays as claimed in claim 1, wherein said diffusion layercomprises plural light diffusion particles and a substrate.
 6. Thestructure of diffusion sheet in the direct type backlight module withanti-UV rays as claimed in claim 5, wherein said light diffusionparticles is selected from one of organic and inorganic materials. 7.The structure of diffusion sheet in the direct type backlight modulewith anti-UV rays as claimed in claim 6, wherein said light diffusionparticles is selected from one of acrylic resin, Titanium Dioxide (TiO₂)and Silicon Dioxide (SiO₂), Silicon.
 8. The structure of diffusion sheetin the direct type backlight module with anti-UV rays as claimed inclaim 5, wherein said substrate is selected from one of acrylic resin,PMMA (Polymethyl Methacrylate), MS (MMA Styrene Copolymer) and PC(Polycarbonate), COC (Cycle Olefin Copolymer).
 9. A method ofmanufacturing diffusion sheet in the direct type backlight module withanti-UV rays comprising the steps of: extruding a diffusion layer byadding a plurality of light diffusion particles into a substrate andusing a first extruder; extrusion a ultra-violet rays absorption layerby adding a ultra-violet rays absorbent into a resin and using a secondextruder; taking said ultra-violet rays absorption layer to touch atleast one surface of said diffusion layer by a multi-layer T-die;co-extruding said diffusion layer and said ultra-violet rays absorptionlayer to form a plate structure of light diffusion sheet withanti-yellow and well dimensional stability.
 10. The structure ofdiffusion sheet in the direct type backlight module with anti-UV rays asclaimed in claim 9, wherein the content of said light diffusionparticles is 1˜10 percent of said substrate.
 11. The structure ofdiffusion sheet in the direct type backlight module with anti-UV rays asclaimed in claim 9, wherein the increment of said ultra-violet raysabsorbent is 1 percent of said resin.
 12. A structure of a diffusionsheet in a direct type backlight module with ultraviolet ray resistance,comprising: a diffusion layer formed by light diffusing particulatesdisbursed in a first resin, said diffusion layer having first and secondopposing sides; and at least one ultraviolet ray absorption layeroverlaying said first side of said diffusion layer, said ultraviolet rayabsorption layer being formed by an ultraviolet ray absorbent disbursedin a second resin.
 13. The structure of a diffusion sheet as claimed inclaim 12, wherein said first and second resin acrylic resin.
 14. Thestructure of a diffusion sheet as claimed in claim 12, wherein saidlight diffusion particulates are formed by particulates of silicon. 15.The structure of a diffusion sheet as claimed in claim 12, wherein saidlight diffusion particulates are formed by particulates of titaniumdioxide (TiO₂).
 16. The structure of a diffusion sheet as claimed inclaim 12, wherein said light diffusion particulates are formed byparticulates of silicon dioxide (SiO₂).
 17. The structure of a diffusionsheet as claimed in claim 12, further comprising a second ultravioletray absorption layer overlaying said second side of said diffusionlayer, said second ultraviolet ray absorption layer being formed by saidultraviolet ray absorbent disbursed in said second resin.
 18. A methodof manufacturing a diffusion sheet in a direct type backlight modulewith ultraviolet ray resistance, comprising the steps of: blending aplurality of light diffusion particles into a first resin using a firstextruder; blending an ultraviolet ray absorbent into a second resinusing a second extruder; coupling an output of each of said firstextruder and said second extruder to a multi-layer T-die; co-extruding adiffusion layer output from said first extruder with at least oneultraviolet absorption layer on at least one side of said diffusionlayer and output from said second extruder to form a plate structure ofa light diffusion sheet with anti-yellowing and dimensional stabilitycharacteristics.